Process for producing multilayered product

ABSTRACT

The present invention is to provide a method of producing multilayer laminates comprising a polyamide and a fluorine-containing ethylenic polymer laminated together and being excellent in interlayer adhesion strength by multilayer coextrusion in an easy and simple manner without need of any additional step or without being limited to some or other particular adhesive material.  
     The present invention is a production method of a multilayer laminate which comprises laminating at least a polyamide (A) and a fluorine-containing ethylenic polymer (B) by simultaneous multilayer coextrusion using a coextrusion apparatus to obtain the laminate comprising said polyamide (A) and said fluorine-containing ethylenic polymer (B), said coextrusion apparatus comprising a die and a plurality of extruders for feeding resins to said die, and the temperature of said die being set within the range exceeding 260° C. but not higher than 310° C.

TECHNICAL FIELD

[0001] The present invention relates to a production method ofmultilayer laminates which comprises laminating a polyamide and afluorine-containing ethylenic polymer by simultaneous multilayercoextrusion.

BACKGROUND ART

[0002] Multilayer laminates formed by laminating a polyamide and afluorine-containing resin are expected as composite materials havingpolyamide characteristics, such as high strength, high toughness, lightweight, good processability and in particular, flexibility, as well asfluorine-containing resin characteristics, such as heat resistance, oiland chemical resistance, and low liquid agent permeability.

[0003] The successive lamination method and simultaneous laminationmethod are known for producing such multilayer laminates. Among them,the simultaneous lamination method, especially coextrusion method holdsan important position because of its merit lying in that the number ofsteps required for obtaining the laminate can be lowered. Thesimultaneous multilayer coextrusion method is applied to multilayermolding or multilayer film formation using two or more extruders and,currently, films, sheets, extruded molded articles called profiles,pipes, hoses, tubes and other moldings varied in shape or form are beingproduced by the method. The method is applicable to variousthermoplastic resins, such as polyamides, as well as tofluorine-containing resins.

[0004] However, fluorine-containing resins are characterized in thatthey are low in intermolecular cohesive force and very low in surfacefree energy because of the low polarizability of fluorine-containingmolecules. Therefore, they can hardly be wet against solids higher inintermolecular cohesive force, hence they show low adhesive propertiesagainst most of other substances. They, as resins, are thuscharacteristically poor in adhesion properties and their interlayeradhesiveness with polyamides is low; it is therefore necessary tocontrive to increase the interlayer adhesion strength. For example,methods are known which comprise subjecting the surface of thefluorine-containing resin to surface treatment such as corona dischargetreatment or irradiation treatment. Japanese Kokai PublicationHei-05-8353, for instance, proposes a method of producing multilayertubes comprising a polyamide resin as an outer layer and afluorine-containing resin as an inner layer by irradiating the tubes tointroduce intermolecular crosslinking structures among molecules in bothlayers and thereby secure the adhesion strength between the polyamideresin layer and the fluorine-containing resin layer. However, the methodcannot be applied to the simultaneous lamination technique includingcoextrusion.

[0005] Also available is a technology according to which a polymer blendcomprising a fluorine-containing resin is used for the resin layer to beadhered to a polyamide. As a production method using this technology,Japanese Kokai Publication Hei-07-53823 discloses a method of producingmultilayer tubes comprising an outer layer comprising a polyamide and aninner layer comprising a fluorine-containing resin in which a resincomposition comprising both a specific polyamide and afluorine-containing resin is laminated to a polyamide layer so that itmay serve as an adhesive layer with the inner layer. In this productionmethod, however, the morphology of the adhesive layer changes accordingto the molding conditions due to the intrinsically poor compatibilitybetween the constituent resins of the adhesive layer, namely thepolyamide and fluorine-containing resin, and the morphology changeinfluences on the cohesive force of the adhesive layer itself and theadhesion strength thereof with the other layers. Thus, such problemsarise as a tendency toward variation in adhesion strength according toenvironmental factors such as molding conditions and temperatureconditions during use and difficulty in securing a constant qualitylevel. Furthermore, this technology does not intend to increase theadhesiveness of the polyamide and fluorine-containing resin themselvesbut merely utilizing the adhesiveness of the polymer blend. In addition,the use of such polymer blend in lieu of the fluorine-containing resinresults in an impairment in those excellent characteristics of thefluorine-containing resin.

[0006] To solve this problem, attempts have been made to improve thefluorine-containing resin itself, and various fluorine-containing resinmaterials have been proposed. For example, in the WO 99/45044 pamphlet,there is disclosed a method of multilayer simultaneous extrusion oflaminates which comprises polyamide 12 (nylon 12) as an outer layer anda fluorine-containing ethylenic polymer having carbonyl groups, such ascarbonate groups and/or carbonyl halide groups, as an inner layerfluorine-containing resin to be laminated to the outer layer. In thismethod, the die temperature is set at 260° C., and an interlayeradhesion strength of ten and several of N/cm and a good appearance canbe obtained. However, such a level of adhesion strength is not fullysufficient in some fields of application.

[0007] Thus, in the art, the efforts to develop production technologiesof improving the performance characteristics of multilayer laminatescomprising a polyamide and a fluorine-containing resin, in particular afluorine-containing ethylenic polymer, can be said to have beenprincipally directed to two aspects, namely investigations concerningthe method of physical treatment of the adhesive surface andcontrivances for adhesive materials, as mentioned above. There is noproduction method known, however, for attaining sufficiently highinterlayer adhesion strength without requiring an additional step orsteps and without being restricted to a specific adhesive material, inparticular for attaining high productivity by applying the simultaneousmultilayer coextrusion technique.

SUMMARY OF THE INVENTION

[0008] In view of the above-mentioned state of the art, it is an objectof the present invention to provide a production method of multilayerlaminates comprising a polyamide and a fluorine-containing ethylenicpolymer laminated together and being excellent in interlayer adhesionstrength by multilayer coextrusion in an easy and simple manner withoutneed of any additional step or without being limited to use of some orother particular adhesive material.

[0009] In those multilayer laminates comprising a polyamide and afluorine-containing resin laminated together which are in the form offilms, sheets, hoses or tubes etc., hence are required to haveflexibility, polyamides having a relatively low melting point, inparticular nylon 11 and nylon 12, are generally used among others. If,in this case, the molding temperatures in multilayer coextrusion, namelythe cylinder temperature and die temperature, are selected at levelsmuch higher than the melting points of the resins, the melt viscosity ofthe resin will become too low, hence molding will become difficult tocarry out. The possibility of resin degradation will also arise.Therefore, in the molding technology field, the molding temperatures areselected at levels which these problems no no more arise. Thus, the dietemperature in extrusion molding of nylon 11 or nylon 12 as so faremployed is within the range of 240 to 250° C. and, even in laminationwith a fluorine-containing resin, a temperature range exceeding 260° C.has never been employed as the die temperature in molding nylon 11 ornylon 12, as described in the above-cited WO 99/45044 pamphlet.

[0010] However, as a result of intensive investigations concerning theinfluences of various multilayer molding conditions in order toaccomplish the above object, the present inventors unexpectedly foundthat when a die temperature in a specific range exceeding thetemperature range conventionally employed is used for lamination bysimultaneous multilayer coextrusion, the above object can beaccomplished and, based on this finding, they have now completed thepresent invention.

[0011] Thus, the present invention relates to a production method of amultilayer laminate which comprises laminating at least a polyamide (A)and a fluorine-containing ethylenic polymer (B) by simultaneousmultilayer coextrusion using a coextrusion apparatus to obtain thelaminate comprising said polyamide (A) and said fluorine-containingethylenic polymer (B), said coextrusion apparatus comprising a die and aplurality of extruders for feeding resins to the die, and thetemperature of said die being set within the range exceeding 260° C.,preferably not lower than 265° C., more preferably not lower than 270°C., but not higher than 310° C., preferably not higher than 300° C.,more preferably not higher than 290° C.

[0012] In accordance with a preferred embodiment of the invention, thetemperature of a feed block, in case that the feed block is connected tothe die, is also set within the range, namely above 260° C. but nothigher than 310° C.

[0013] In a preferred embodiment of the invention, a cylindertemperature of the extruder for feeding the polyamide (A) to said die isset at a level higher by 20 to 90° C. than the melting point of thepolyamide (A), or the temperature of the polyamide (A) at a resin inlet,connected to the extruder, of the die, or of the feed block, in casethat the feed block is connected to the die, is set at a level higher by20 to 90° C. than the melting point of the polyamide (A).

[0014] In a preferred embodiment of the invention, the above polyamide(A) is nylon 11 or nylon 12.

[0015] In a preferred embodiment of the invention, thefluorine-containing ethylenic polymer (B) is a fluorine-containingethylenic polymer having carbonyl group with a carbonyl group content of3 to 1,000 groups, in total, per 1×10⁶ main chain carbon atoms.

[0016] In a preferred embodiment of the invention, the simultaneousmultilayer coextrusion is carried out by a technique selected from thegroup consisting of a multilayer film coextrusion, multilayer sheetcoextrusion, multilayer blow coextrusion, multilayer profilecoextrusion, multilayer pipe coextrusion, multilayer tube coextrusion,multilayer wire coating coextrusion and multilayer steel pipe coatingcoextrusion techniques.

[0017] In a preferred embodiment of the invention, the abovesimultaneous multilayer coextrusion technique is carried out by atechnique selected from the group consisting of a lamination techniquein front of the die, a lamination technique within the die and alamination technique behind the die, in which resins to be coextrudedare joined for multilayer formation in front of the die, within the dieand behind the die, respectively. The above die may be a flat die or acircular die, preferably a circular die in which resin spreading iseffected by a type selected from the group consisting of spider,crosshead and spiral types.

[0018] The present invention also relates to an automotive fuel pipingtube or hose each having an at least three-layer structure comprising,as an outer layer, a layer comprising a polyamide (A); as anintermediate layer, a layer comprising a fluorine-containing ethylenicpolymer (B); and, as an inner layer, a layer (C) comprising afluorine-containing resin and containing or not containing anelectrically conductive material, said fluorine-containing resin havinga melting point not lower than 250° C.

[0019] The present invention further relates to an automotive fuelpiping tube or hose each having an at least four-layer structurecomprising, as an outer layer, a layer comprising a polyamide (A); as anintermediate layer, a layer comprising a fluorine-containing ethylenicpolymer (B); a layer (C) comprising a fluorine-containing resin and notcontaining an electrically conductive material; and, as an innermostlayer, a layer (D) comprising a fluorine-containing resin and containingan electrically conductive material, wherein at least one of thefluorine-containing resin of the layer (C) and the fluorine-containingresin of the layer (D) has a melting point not lower than 250° C.

DETAILED DISCLOSURE OF THE INVENTION

[0020] In the following, the present invention is described in detail.

[0021] In carrying out simultaneous multilayer coextrusion according tothe production method of the invention, a coextrusion apparatuscomprising a die and a plurality of extruders respectively feeding, tothe die, at least a polyamide (A) and a fluorine-containing ethylenicpolymer (B), where necessary together with another resin or other resinsis used. In the following, this apparatus is first described in detail.

Coextrusion Apparatus

[0022] Industrially, the above-mentioned simultaneous multilayercoextrusion is carried out using a coextrusion apparatus having aconstitution comprising a die and a plurality of extruders feedingresins mentioned above to the die. Generally, the coextrusion apparatusmay have a constitution comprising a plurality of extruders to bedescribed below in detail which feed the above-mentioned raw materialresins to the die, the die, a cooling apparatus for cooling and shaping(sizing) the resins that have passed through the die(s), a treatmentsystem disposed when necessary for corona treatment, flame treatment,ozone treatment and/or the like, and a take-up unit of a molded article.

1. Extruders

[0023] As the above extruders, the plurality of extruders is generallydisposed for feeding the raw material resins for forming the respectivelayers, and the number thereof is equal to the number of the constituentlayers. However, it is not always necessary for the number of extrudersto be equal to the number of the constituent layers. Any knownconstitution capable of feeding the specified resins to each die can beemployed. The fundamental structure of the extruder is not particularlyrestricted but preferably is of the screw type. The screw extrudergenerally comprises an adapter (connecting part between the extruder anddie), screw, cylinder, hopper, and cylinder temperature control unit.The above screw extruder may be a single-screw extruder or a twin-screwextruder. Generally, a single-screw extruder is used. The extruder maybe provided with a vent hole so that the volatile substances generatedfrom the resin may be excluded upon opening the vent hole or reducingthe pressure through it. The respective raw material resins sufficientlymelted in the extruders are then fed to a die, or to the so-called feedblock when such block is connected to the die for joining resins to becoextruded for multilayer formation in front of the die. Therefore, theraw material resins are fed to the die from the extruders via theadapter, or via the feed block from the adaptor when the feed block isconnected to the die. The resins may also be fed from the extruder tothe die or feed block via a gear pump in order to maintain the extrusionoutput at a constant level and thereby control the thickness of moldedarticles more precisely.

2. Die

[0024] The die may appropriately be selected according to theapplication use. For example, a flat die or a circular die (forinflation films) may be used in molding multilayer films or sheets, apipe or tube die (circular die) in molding multilayer pipes or tubes, ablow die in multilayer blow molding, a profile die in multilayer profilemolding, a wire coating die in molding multilayer wire coatings, or apipe coating die in molding multilayer steel pipe coatings.

[0025] When a molten resin is fed to this die, the resin is spread inthe flow channel within the die. The manner of spreading may be, forexample, by the spider method, by the cross head method enablingextrusion in a direction 90° to the extruder, or by the spiral method.Among these, the spiral method is preferred since a uniform layerthickness can be obtained thereby.

[0026] The length of the flat portion of a die mandrel of the circulardie can appropriately be selected and may be about 50 to 200 mm, forinstance.

[0027] Meanwhile, in carrying out simultaneous multilayer coextrusion,it is necessary to join the respective resin layers constitutingmultilayer in a coextrusion apparatus for multilayer formation. Theposition of joining the resin layers fed from the respective extrudersfor multilayer formation is preferably within the die but may be any ora combination of the modes mentioned below.

[0028] i) Lamination technique in front of the die which comprisesjoining the resins before their entering the die in a block called feedblock (also called combining adapter): In this technique, a block calledfeed block is disposed on the side upstream of the die (single manifolddie). The raw material resins constituting respective layers are firstfed from the respective extruders to this block and, after joining forlamination, they are fed from the feed block to the die.

[0029] ii) Lamination technique within the die which comprises joiningthe resins within the die for multilayer formation: In this technique,the respective layer-constituting raw material resins are fed from therespective extruders to a die (multi-manifold die) having a plurality ofresin wells called manifold and caused to join immediately upstream ofthe so-called lip within the die for multilayer formation.

[0030] iii) Lamination technique behind the die: In this technique, adie (dual slot die) having a plurality of separated flow channels isused. The raw material resins constituting respective layers are fedfrom the respective extruders and passed through the die each in aseparated state and, thereafter, they are joined for multilayerformation.

[0031] In the production method according to the invention, thetemperature of the above die is set at a level within the range of above260° C., preferably not lower than 265° C., more preferably not lowerthan 270° C., but not higher than 310° C., preferably not higher than300° C., more preferably not higher than 290° C. Therefore, it mayappropriately be set at 265 to 300° C., more preferably 270 to 290° C.At a die temperature below 260° C., it is impossible to obtainsufficiently high interlayer adhesion strength and, at above 310° C.,the resins undergo marked thermal degradation and the multilayerlaminates obtained thus show decreased strength and elongation and apoor appearance. Thus, the temperature is limited within the aboverange.

[0032] When a feed block is connected to the die (the above mode i), itis preferred that not only the die temperature but also the temperatureof the feed block be set at a level within the range of above 260° C.,preferably not lower than 265° C., more preferably not lower than 270°C., but not higher than 310° C., preferably not higher than 300° C.,more preferably not higher than 290° C. In this case, it is preferredthat the die and feed block should be at the same temperature.

[0033] In the production method according to the invention, it ispreferred that the cylinder temperature of the extruder for feeding thepolyamide (A) to the above die be higher by 20 to 90° C. than themelting point of the polyamide (A) or that the temperature of thepolyamide (A) at the resin inlet (adapter section), which is connectedto the extruder, of the die (the above mode ii or iii) or of the feedblock (the above mode i) in case that the feed block is connected to thedie, be higher by 20 to 90° C. than the melting point of the polyamide(A). At lower temperatures than this temperature, no good moldings maypossibly be obtained due to insufficient melting of the resin and, athigher temperatures than this temperature, the resin may possiblyundergo thermal degradation and the tensile strength and elongation ofthe moldings, such as tubes, may decrease in some instances. Morepreferably, the temperature in question is set at a level higher by 30to 80° C. than the melting point of the polyamide (A). In this case, thedifference between the cylinder temperature and the above dietemperature is relatively small, so that there is no possibility of itscausing a marked increase in resin pressure in the die.

[0034] Now, the polyamide (A) and fluorine-containing ethylene polymer(B) to be used in the practice of the invention are described in detail.

Polyamide (A)

[0035] The polyamide so referred to herein means a crystallinemacromolecule having the amide bond —NH—CO— in a repeating unit withinthe molecule. As such, there may be mentioned, for example, theso-called nylon resins, namely resins in which a majority of amide bondsare bound to an aliphatic or alicyclic structure. Specifically, theremay be mentioned, for example, nylon 6, nylon 66, nylon 11, nylon 12,nylon 610, nylon 612, nylon 46, metaxylylenediamine/adipic acidpolymers, nylon 6/66 copolymers, and nylon 66/12 copolymers, and blendsof these.

[0036] The polyamide to be used in the practice of the invention mayhave a structure having no amide bond in a repeating unit as partiallyoccurring within the polyamide in a block or graft form. As such resin,there may be mentioned the polyamide elastomers such as nylon6/polyester copolymers, nylon 6/polyether copolymers, nylon 12/polyestercopolymers and nylon 12/polyether copolymers. These polyamide elastomersare block copolymers resulting from copolymerization of nylon resinoligomers and polyester resin oligomers or polyether resin oligomers byforming ester bonding or ether bonding. The above polyester resinoligomers include, for example, polycaprolactone and polyethyleneadipate, and the polyether resin oligomers include, for example,polyethylene glycol, polypropylene glycol and polytetramethylene glycol.Particularly preferred embodiments are nylon 6/polytetramethylene glycolcopolymers and nylon 12/polytetramethylene glycol copolymers.

[0037] In the practice of the present invention, the polyamide ispreferably selected from among appropriate species having a meltingpoint of not lower than 130° C., more preferably not lower than 150° C.When the melting point is lower than 130° C., the layer formed therefrommay be poor in mechanical properties, heat resistance or the like.

[0038] For use in the practice of the invention, the polyamidepreferably has a relative viscosity which indicates a molecular weightof not less than 1.8, more preferably not less than 2.0. When it is lessthan 1.8, the resin may show poor moldability, giving moldings inferiorin mechanical properties. On the other hand, the upper limit ispreferably not more than 4.0. If it exceeds 4.0, the polymerization ofthe resin itself is difficult and, even if the resin is obtained, theresin may be poor in moldability. The above-mentioned relative viscosityis determined as described in JIS K 6810.

[0039] Usable as the polyamide in the practice of the invention is anyof nylon 11, nylon 12, nylon 610, nylon 612, a nylon 6/polyethercopolymer or a nylon 12/polyether copolymer in the case of producingtube or hose moldings, which are required to have toughness. When themoldings are expected to be used in automotive fuel piping, nylon 11 andnylon 12 are more preferred among others in view of the occurrence ofzinc chloride water sprinkled over roads as a snow melting agent.

[0040] In the practice of the invention, the above polyamide maycontain, in addition to the amide group, a functional group or groupsselected from the group consisting of hydroxyl group, carboxyl group,ester group and sulfonamide group in a total amount of 0.05 to 80equivalent percent relative to the amide group. When it contains one ormore species among hydroxyl group, carboxyl group, ester group andsulfonamide group in a total amount such that the above conditionrelative to the amide groups may be satisfied, the initialcharacteristics of the interlayer adhesion strength with thefluorine-containing ethylenic polymer (B) can favorably be maintainedover a prolonged period of time without those characteristics beingimpaired. Among the functional groups mentioned above, a sulfonamidegroup is preferred and it is particularly preferred that the polyamidecontains a sulfonamide group or groups directly bound to an aromaticring. The total content of the functional group(s) other than the amidegroup is preferably 1 to 70 equivalent percent, more preferably 1 to 50equivalent percent, relative to the amide group.

[0041] Such a polyamide as mentioned above may be one resulting fromcopolymerizing a copolymerizable monomer having such a functional groupor groups with the polyamide-based resin in such an amount that theabove-mentioned content of the functional group(s) can be attained, orincorporating a plasticizer having at least one functional group speciesselected from the group consisting of hydroxyl group, carboxyl group,ester group and sulfonamide group or a macromolecule having such afunctional group(s) and compatible with the polyamide so that theabove-mentioned functional group content may be attained. Theabove-mentioned macromolecule having such a functional group(s) andcompatible with the polyamide includes, for example, ester- and/orcarboxylic acid-modified olefinic resins (ethylene/methyl acrylatecopolymers, ethylene/acrylate copolymers, ethylene/methylacrylate/maleic anhydride copolymers, ethylene/ethyl acrylatecopolymers, propylene/maleic anhydride copolymers, etc.), ionomerresins, polyester resins, phenoxy resins, ethylene-propylene-dienecopolymers, and polyphenylene oxide.

[0042] Among them, the method comprising incorporating a plasticizer isadvantageous in that not only the desired amount of the above-mentionedfunctional group(s) can be incorporated at a relatively low additionlevel but also the effects intrinsic in the plasticizer can be shown inrendering the resin composition flexible and improving the coldtemperature mechanical properties of tubes or hoses, in particular. Inthis case, the addition level may vary depending on the plasticizerspecies. Generally, however, the above functional group content can beattained at an addition level of about 5 to 20% by weight relative tothe whole amount of the composition.

[0043] As such plasticizers, there may be mentioned, for example,alcoholic hydroxyl group-containing compounds such as hexylene glycoland glycerol; phenolic hydroxyl group-containing compounds such asβ-naphthol, dibenzylphenol, octylcresol, bisphenol A and like bisphenolcompounds, octyl p-hydroxybenzoate, 2-ethylhexyl p-hydroxybenzoate andheptyl p-hydroxybenzoate; carboxyl group-containing compounds such asp-hydroxybenzoic acid-ethylene oxide and/or propylene oxide adducts;ester group-containing compounds such as octyl p-hydroxybenzoate,2-ethylhexyl p-hydroxybenzoate, heptyl p-hydroxybenzoate and likebenzoic acid esters and, further, ε-caprolactone, phosphate esters ofphenolic compounds, and the like; and sulfonamide group-containingcompounds such as N-methylbenzenesulfonamide, N-ethylbenzenesulfonamide,N-butylbenzenesulfonamide, toluenesulfonamide, N-ethyltoluenesulfonamideand N-cyclohexyltoluenesulfonamide.

[0044] In this case, the amine value of the polyamide in which theplasticizer is incorporated is not particularly restricted. In the caseof ordinary polyamides, the value is generally less than 10equivalents/10⁶ g, and such polyamides can be used. Polyamides havinggreater amine values, for example within the range of 10 to 60equivalents/10⁶ g, can also be used. Meanwhile, from the viewpoint ofmolecular weight or adhesion strength, the polyamide preferably has anacid value not higher than 80 equivalents/10⁶ g.

[0045] In the practice of the present invention, the polyamide maycontain another resin, a colorant and/or one or more of variousadditives unless the object of the invention is deteriorated. As theadditives, there may be mentioned, for example, antistatic agents, flameretardants, heat stabilizers, ultraviolet absorbers, lubricantsmold-release agents, nucleating agents, and reinforcing agents(fillers).

Fluorine-Containing Ethylenic Polymer (B)

[0046] The fluorine-containing ethylenic polymer according to theinvention may comprise a homopolymer chain or copolymer chain having therepeating unit derived from at least one fluorine-containing ethylenicmonomer species, and the polymer chain may be one resulting frompolymerization of a fluorine-containing ethylenic monomer or monomersalone or from polymerization of a fluorine-containing ethylenic monomeror monomers and a fluorine atom-free ethylenic monomer or monomers.

[0047] The above-described fluorine-containing ethylenic monomer is afluorine atom-containing, olefinically unsaturated monomer andspecifically includes tetrafluoroethylene, vinylidene fluoride,chlorotrifluoroethylene, vinyl fluoride, hexafluoropropylene,hexafluoroisobutene, monomers represented by the formula (ii):

CH₂═CX¹(CF₂)_(n)X²   (ii)

[0048] in the formula, X¹ is H or F, X² is H, F or Cl and n is aninteger of 1 to 10, perfluoro(alkyl vinyl ether) compounds and the like.

[0049] The above-described fluorine atom-free ethylenic monomer ispreferably selected from among ethylenic monomers containing not morethan 5 carbon atoms so that the heat resistance, chemical resistance andlike characteristics may not be reduced. Specifically, there may bementioned ethylene, propylene, 1-butene, 2-butene, vinyl chloride,vinylidene chloride, etc.

[0050] In cases where a fluorine-containing ethylenic monomer(s) and afluorine atom-free ethylenic monomer(s) are used, the monomercomposition may have a ratio of 10 to 100 mole percent (e.g. 30 to 100mole percent) of the fluorine-containing ethylenic monomer(s) to 90 to 0mole percent (e.g. 70 to 0 mole percent) of the fluorine atom-freeethylenic monomer(s).

[0051] By selecting the fluorine-containing ethylenic monomer speciesand fluorine atom-free ethylenic monomer species, and the combinationand composition ratio thereof, the melting point or glass transitionpoint of the fluorine-containing ethylenic polymer according to theinvention can be adjusted and the polymer may be either resin-like orelastomer-like. The form and properties of the fluorine-containingethylenic polymer can appropriately be selected according to theperformance characteristics required of and the application field of themultilayer laminate. It is preferred, among others, that the polymer hasa melting point of 150 to 270° C. Such polymer can fully show theadhesion properties of its carbonyl groups and can advantageouslyprovide firm adhesion strength when laminated directly together with theother material. For enabling lamination also with an organic materialhaving relatively low heat resistance, the melting point is morepreferably not higher than 230° C., still more preferably not higherthan 210° C.

[0052] As for the molecular weight of the fluorine-containing ethylenicpolymer to be used according to the invention, it is preferably withinsuch a range that the polymer can be molded at temperatures below theheat decomposition point and that the moldings obtained can displaythose excellent mechanical properties, chemical resistance and otherproperties which are intrinsic in the fluorine-containing ethylenicpolymer. More specifically, when the melt flow rate (MFR) is taken as anindex of molecular weight, the MFR at an arbitrary temperature withinthe range of about 230 to 300° C. is preferably 0.5 to 100 g/10 minutes.

[0053] Preferred as the fluorine-containing ethylenic polymer accordingto the invention is a fluorine-containing ethylenic polymer comprisingthe tetrafluoroethylene unit from the viewpoint of heat resistance andchemical resistance, or, from the viewpoint of moldability/workability,a fluorine-containing ethylenic copolymer comprising the vinylidenefluoride unit.

[0054] As preferred typical examples of the fluorine-containingethylenic polymer according to the invention, there may be mentionedfluorine-containing ethylenic copolymers (I) to (V) whosefluorine-containing ethylenic polymer chain is a polymer chainessentially resulting from polymerization of the monomers mentionedbelow:

[0055] (I) copolymers resulting from polymerization at least of 5 to 95mole percent of tetrafluoroethylene and 95 to 5 mole percent ofethylene;

[0056] (II) copolymers resulting from polymerization at least of 3 to 97mole percent of tetrafluoroethylene and 97 to 3 mole percent of acompound represented by the general formula:

CF₂═CF-Rf¹

[0057] in the formula, Rf¹ represents CF₃ or ORf² and Rf² represents aperfluoroalkyl group having 1 to 5 carbon atoms;

[0058] (III) copolymers resulting from polymerization at least of thefollowing a, b and c:

[0059] a. 20 to 90 mole percent, preferably 20 to 70 mole percent, oftetrafluoroethylene;

[0060] b. 10 to 80 mole percent, preferably 20 to 60 mole percent, ofethylene; and

[0061] c. 1 to 70 mole percent, preferably 1 to 60 mole percent, of acompound represented by the general formula:

CF₂═CF-Rf¹

[0062] in the formula, Rf¹ represents CF₃ or ORf² and Rf² represents aperfluoroalkyl group having 1 to 5 carbon atoms;

[0063] (IV) copolymers resulting from polymerization of at leastvinylidene fluoride; and

[0064] (V) copolymers resulting from polymerization at least of thefollowing d, e and f:

[0065] d. 15 to 60 mole percent of vinylidene fluoride;

[0066] e. 35 to 80 mole percent of tetrafluoroethylene; and

[0067] f. 5 to 30 mole percent of hexafluoropropylene.

[0068] The fluorine-containing ethylenic polymers specifically mentionedabove are all preferred in view of their good heat resistance, chemicalresistance, weathering resistance, and electrical insulating andnon-stick properties.

[0069] As the copolymers (I) mentioned above, there may morespecifically be mentioned, for example, copolymers comprising 20 to 90mole percent (e.g. 20 to 60 mole percent) of the tetrafluoroethyleneunit, 10 to 80 mole percent (e.g. 20 to 60 mole percent) of the ethyleneunit and 0 to 70 mole percent of the unit derived from a monomercopolymerizable with these.

[0070] The copolymerizable monomer mentioned above includeshexafluoropropylene, chlorotrifluoroethylene, monomers represented bythe formula (ii):

CH₂═CX¹(CF₂)_(n)X²   (ii)

[0071] in the formula, X¹ is H or F, X² is H, F or Cl and n is aninteger of 1 to 10, perfluoro(alkyl vinyl ether) compounds, propyleneand the like. One or more of these are generally used.

[0072] Such fluorine-containing ethylenic polymers are preferred becauseof their good heat resistance, chemical resistance, weatheringresistance, and electrical insulating and non-stick properties, inparticular.

[0073] Preferred among these are the following:

[0074] (I-1) copolymers comprising 62 to 80 mole percent of thetetrafluoroethylene unit, 20 to 38 mole percent of the ethylene unit and0 to 10 mole percent of the unit derived from another monomer; and

[0075] (I-2) copolymers comprising 20 to 80 mole percent of thetetrafluoroethylene unit, 10 to 80 mole percent of the ethylene unit, 0to 30 mole percent of the hexafluoropropylene unit and 0 to 10 molepercent of the unit derived from another monomer.

[0076] These copolymers retain the excellent performance characteristicsof tetrafluoroethylene/ethylene copolymers, can have a relatively lowmelting point and can maximally display their adhesiveness to othermaterials, hence are preferred.

[0077] Preferred as the above-mentioned copolymer (II) are, for example,

[0078] (II-1) copolymers comprising 65 to 95 mole percent, preferably 75to 95 mole percent, of the tetrafluoroethylene unit and 5 to 35 molepercent, preferably 5 to 25 mole percent, of the hexafluoropropyleneunit;

[0079] (II-2) copolymers comprising 70 to 97 mole percent of thetetrafluoroethylene unit and 3 to 30 mole percent of the CF₂═CF—ORf²unit (Rf² being a perfluoroalkyl group having 1 to 5 carbon atoms); and

[0080] (II-3) copolymers comprising the tetrafluoroethylene unit,hexafluoropropylene unit and CF₂═CF—ORf² unit (Rf² being as definedabove), in which the hexafluoropropylene unit and CF₂═CF—ORf² unitaccount for 5 to 30 mole percent in total.

[0081] The above (II-1) to (II-3) are the perfluoro type copolymers andare most excellent in heat resistance, chemical resistance, waterrepellency, and non-stick, electric insulating and other properties,among fluorine-containing ethylenic polymers.

[0082] As the above-mentioned copolymers (IV), there may be mentioned,for example, copolymers comprising 15 to 99 mole percent of thevinylidene fluoride unit, 0 to 80 mole percent of thetetrafluoroethylene unit and 0 to 30 mole percent of the unit derivedfrom at least one of hexafluoropropylene and chlorotrifluoroethylene.

[0083] More specifically, there may be mentioned, for example, thefollowing:

[0084] (IV-1) copolymers comprising 30 to 99 mole percent of thevinylidene fluoride unit and 1 to 70 mole percent of thetetrafluoroethylene unit;

[0085] (IV-2) copolymers comprising 60 to 90 mole percent of thevinylidene fluoride unit, 0 to 30 mole percent of thetetrafluoroethylene unit and 1 to 20 mole percent of thechlorotrifluoroethylene unit;

[0086] (IV-3) copolymers comprising 60 to 99 mole percent of thevinylidene fluoride unit, 0 to 30 mole percent of thetetrafluoroethylene unit and 5 to 30 mole percent of thehexafluoropropylene unit; and

[0087] (IV-4) copolymers comprising 15 to 60 mole percent of thevinylidene fluoride unit, 35 to 80 mole percent of thetetrafluoroethylene unit and 5 to 30 mole percent of thehexafluoropropylene unit.

[0088] In the practice of the invention, it is particularly preferredthat the fluorine-containing ethylenic polymer contains a carbonylgroup(s) so that its adhesiveness to the layer comprising the polyamide(A) may become more firm and strong.

[0089] The term “carbonyl group” as used herein means a functional grouphaving —C(═O)— essentially reactive with such functional groups as amidegroup and amino group in the above-mentioned polyamide (A). Morespecifically, it includes carbonate, carbonyl halide, aldehyde, ketone,carboxyl, ester, acid anhydride, isocyanate and the like. On thecontrary, amide, imide, urethane, urea and the like, in spite of theirhaving —C(═O)—, are poor in reactivity as compared with the carbonategroup and other functional groups mentioned above, hence may be said tobe essentially incapable of reacting with the functional groups in theabove-mentioned polyamide (A). Preferred as the carbonyl group in thepractice of the invention are carbonate group, carbonyl halide group andcarboxyl group, which can be introduced with ease and are highlyreactive with the polyamide (A).

[0090] The number of carbonyl groups in the fluorine-containingethylenic polymer according to the invention may appropriately beselected according to the other material to be laminated, the shape, theapplication field of the multilayer laminate, the adhesion strengthrequired, the form of said polymer, etc. It is preferred, however, thatthe number of carbonyl groups should be 3 to 1,000, in total, per 1×10⁶main chain carbon atoms. When the number of carbonyl groups per 1×10⁶main chain carbon atoms is less than 3, a sufficient adhesion strengthmay not be attained. When it exceeds 1,000, the adhesion strength may bereduced as a result of chemical modification of the carbonyl groups inthe step of adhesion. More preferably, the number is 3 to 500, stillmore preferably 10 to 300. The carbonyl group content in thefluorine-containing ethylenic polymer can be determined by infraredabsorption spectrophotometry.

[0091] Where 20 or more carbonyl halide groups, which are particularlyexcellent in reactivity with the polyamide (A), are present in thefluorine-containing ethylenic polymer per 1×10⁶ main chain carbon atoms,good adhesion to the polyamide (A) can be attained even when the totalcarbonyl group content is less than 150 per 1×10⁶ main chain carbonatoms.

[0092] When the fluorine-containing ethylenic polymer described above isheated, for instance, in the step of molding, or with the lapse of time,the carbonyl halide groups may be decomposed to form carboxylic acid.Therefore, the fluorine-containing ethylenic polymer in the multilayerlaminate generally contains not only the above-mentioned carbonategroups and/or carbonyl halide groups but also carboxyl groups derivedfrom the carbonyl halide groups when these are contained.

[0093] The carbonate groups in the fluorine-containing ethylenic polymeraccording to the invention are groups generally having the bonding—OC(═O)O— and specifically have a structure of —OC(═O)O—R [wherein R isan organic group (e.g. C₁-C₂₀ alkyl group (in particular C₁-C₁₀ alkylgroup), an ether bond-containing C₂-C₂₀ alkyl group or the like) or agroup VII element]. As preferred examples of the carbonate group, theremay be mentioned —OC(═O)OCH₃, —OC(═O)OC₃H₇, —OC(═O)OC₈H₁₇,—OC(═O)OCH₂CH₂CH₂OCH₂CH₃ and the like.

[0094] The carbonyl halide groups in the fluorine-containing ethylenicpolymer according to the invention specifically have a structure of —COY[Y being a halogen element], and examples are —COF and —COCl.

[0095] The fluorine-containing ethylenic polymer having such carbonylgroups itself can retain those excellent characteristics whichfluorine-containing materials have, such as chemical resistance, liquidagent resistance, weathering resistance, and antifouling and non-stickproperties, and can provide the molded laminate with such excellentcharacteristics of fluorine-containing materials without deteriorationthereof.

[0096] In the case where the fluorine-containing ethylenic polymeraccording to the invention contains carbonyl groups within the polymerchain, the mode in which the carbonyl groups are contained in thepolymer chain is not particularly restricted but, for example, carbonylgroups may be bound to the polymer chain termini or side chains.

[0097] Among them, carbonyl groups occurring at polymer chain terminiare preferred since they will not markedly reduce the heat resistance,mechanical properties and chemical resistance or since they areadvantageous from the viewpoint of productivity and cost. A method ofintroducing carbonyl groups into polymer chain termini using apolymerization initiator having a carbonyl group(s) or a functionalgroup(s) convertible to a carbonyl group(s), for example a peroxycarbonate or peroxy ester is preferred embodiment since introduction canbe realized very easily and the content of carbonyl groups introducedcan be controlled with ease. The carbonyl group derived from a peroxideso referred to herein means a carbonyl group directly or indirectlyderived from a functional group contained in a peroxide.

[0098] Even when a fluorine-containing ethylenic polymer having nocarbonyl groups is contained in the fluorine-containing ethylenicpolymer according to the invention, the only requirement is that thetotal number of carbonyl groups per 1×10⁶ main chain carbon atoms on thewhole polymer basis should be within the range described above.

[0099] The production method of the fluorine-containing ethylenicpolymer according to the invention is not particularly restricted butmay comprise subjecting the monomer or monomers corresponding to thedesired fluorine-containing polymer in species and mixing ratio toradical polymerization or ionic polymerization.

[0100] As for the method of radical polymerization, the technique ofsuspension polymerization in an aqueous medium using afluorine-containing solvent and, as polymerization initiator, a peroxycarbonate or the like is preferred from the industrial viewpoint.However, other polymerization methods, for example solutionpolymerization, emulsion polymerization and bulk polymerization, canalso be employed. In suspension polymerization, a fluorine-containingsolvent may be used in addition to water. Usable as thefluorine-containing solvent in suspension polymerization arehydrochlorofluoroalkanes (e.g. CH₃CClF₂, CH₃CCl₂F, CF₃CF₂CCl₂H,CF₂ClCF₂CFHCl), chlorofluoroalkanes (e.g. CF₂ClCFClCF₂CF₃,CF₃CFClCFClCF₃), and perfluoroalkanes (e.g. perfluorocyclobutane,CF₃CF₂CF₂CF₃, CF₃CF₂CF₂CF₂CF₃, CF₃CF₂CF₂CF₂CF₂CF₃). Among them,perfluoroalkanes are preferred. In view of the suspensibility andeconomy, the fluorine-containing solvent is preferably used in an amountof 10 to 100% by weight relative to water.

[0101] The polymerization temperature is not particularly restricted butmay be 0 to 100° C. The polymerization pressure is to be selectedaccording to the species, amount and vapor pressure of the solventemployed, the polymerization temperature and other polymerizationconditions. Generally, it may be 0 to 9.8 MPaG.

[0102] For molecular weight adjustment, conventional chain transferagents can be used, for example hydrocarbons such as isopentane,n-pentane, n-hexane and cyclohexane; alcohols such as methanol andethanol; and halogenated hydrocarbons such as carbon tetrachloride,chloroform, methylene chloride and methyl chloride.

[0103] As a method of obtaining the above-described fluorine-containingethylenic polymer having the carbonyl group, there may be mentioned themethod comprising subjecting a carbonyl group-containing monomer tocopolymerization. As appropriate examples of the carbonylgroup-containing ethylenic monomer, there may be mentionedfluorine-containing monomers such as perfluoroacryloyl fluoride,1-fluoroacryloyl fluoride, acryloyl fluoride, 1-trifluoromethacryloylfluoride and perfluorobutenoic acid and fluorine-free monomers such asacrylic acid, methacrylic acid, acryloyl chloride and vinylenecarbonate. The polymer may also be obtained by subjecting afluorine-containing ethylenic polymer, a grafting compound having acarbonyl group-containing functional group, and a radical generator suchas a peroxide to grafting under melting and mixing at a temperature atwhich radical generation occurs in the extruder.

[0104] On the other hand, while various methods can be employed forproducing fluorine-containing ethylenic polymers having a carbonyl groupor groups at a polymer molecule terminus or termini, the methodcomprising using a peroxide, in particular a peroxy carbonate or aperoxy ester, as the polymerization initiator can preferably be employedfrom the economical viewpoint and the quality viewpoint, for exampleheat resistance and chemical resistance. By this method, it is possibleto introduce, into a polymer chain terminus or termini, carbonyl groupsderived from a peroxide, for example carbonate groups derived from aperoxy carbonate, ester groups derived from a peroxy ester, or carbonylhalide groups derived therefrom by functional group conversion. Amongsuch polymerization initiators, peroxy carbonates can lower thepolymerization temperature without involvement of side reactions in theinitiation reaction, hence are preferably used.

[0105] Preferably used as the above peroxy carbonates are compoundsrepresented by the following formulas (1) to (4):

[0106] In the above formulas, R and R′ each represents a straight orbranched, saturated univalent hydrocarbon group having 1 to 15 carbonatoms or an alkoxy group-terminated, straight or branched, saturatedunivalent hydrocarbon group having 1 to 15 carbon atoms and R″represents a straight or branched, saturated divalent hydrocarbon grouphaving 1 to 15 carbon atoms or an alkoxy group-terminated straight orbranched, saturated divalent hydrocarbon group having 1 to 15 carbonatoms.

[0107] Particularly preferred among others are diisopropylperoxydicarbonate, di-n-propyl peroxydicarbonate, tert-butylperoxyisopropyl carbonate, bis(4-tert-butylcyclohexyl) peroxydicarbonate,di-2-ethylhexyl peroxydicarbonate and the like.

[0108] The amount of the initiator to be used, for example a peroxycarbonate or a peroxy ester, may vary depending on the desired polymerspecies (e.g. composition), molecular weight, polymerization conditionsand the initiator species employed. Generally, however, it is preferably0.05 to 20 parts by weight, in particular 0.1 to 10 parts by weight, per100 parts of the polymer to be obtained by the polymerization.

[0109] The terminal carbonate group or ester group content can becontrolled not only by the use of such a polymerization initiator as aperoxy carbonate or peroxy ester but also by adjusting thepolymerization conditions such as the amount of the chain transfer agentused and the polymerization temperature.

[0110] Various methods can be employed for obtaining fluorine-containingethylenic polymers having a carbonyl halide group or groups at a polymermolecule terminus or termini. For example, such polymers can be obtainedby heating, for causing thermal decomposition (decarboxylation) of theabove-mentioned fluorine-containing ethylenic polymers having carbonategroup(s) or ester group(s) at a terminus or termini, as mentioned above.The heating temperature depends on the carbonate group or ester groupspecies and the fluorine-containing ethylenic polymer species.Preferably, heating is made so that the temperature of the polymeritself may reach 270° C. or above, preferably 280° C. or above, mostpreferably 300° C. or above. The upper limit to the heating temperatureis preferably not higher than the thermal decomposition temperature ofother sites than the carbonate group or ester group of thefluorine-containing ethylenic polymer and, more specifically, not higherthan 400° C., more preferably not higher than 350° C.

[0111] The fluorine-containing ethylenic polymer according to theinvention is preferably used alone so that the adhesiveness, heatresistance and chemical resistance, intrinsic in itself may not beimpaired. According to the intended purpose and use, however, one ormore of various fillers, such as inorganic powders, glass fiber, carbonfiber, metal oxides and carbon may be incorporated therein at levelswhich will not deteriorate the performance characteristics thereof. Inaddition to the fillers, one or more of pigments, ultraviolet absorbersand other optional additives may be formulated. It is also possible toincorporate, in addition to such additives, a resin, for example anotherfluororesin or a thermoplastic or thermosetting resin, a syntheticrubber or the like to thereby improve the mechanical properties andweathering resistance, provide decorativeness, prevent electrostaticcharging, improve the moldability, and so on. In particular,incorporation of an electrically conductive material, such as carbonblack or acetylene black, is of advantage in preventing electrostaticcharge accumulation on such products as tubes and hoses in fuel pipingsystems, hence is preferred.

[0112] The layer comprising the fluorine-containing ethylenic polymer(B) according to the invention comprises the above-describedfluorine-containing ethylenic polymer and another or other componentsincorporated according to need and, where necessary, the layercomprising the above fluorine-containing ethylenic polymer (B) may beelectrically conductive. The term “electrically conductive” as usedherein means that while electrostatic charge may accumulate uponcontinuous soaking of an insulating material such as a resin with aninflammable fluid such as gasoline, whereby the possibility ofinflammation arises, the layer has an electrical property such that thiselectrostatic charge accumulation will not occur. It is provided in SAEJ2260, for instance, that the surface resistivity should be not higherthan 10⁶ Ω/□. For making the layer comprising the above (B) electricallyconductive, the above-described electrically conductive material isincorporated preferably at a level not more than 20% by weight, morepreferably not more than 15% by weight, in the composition constitutingthe above layer. The lower limit is such a level that can provide thesurface resistivity described above.

[0113] In the practice of the present invention, the layer comprisingthe above fluorine-containing ethylenic polymer (B) may be furtherlaminated to a layer (C) comprising a fluorine-containing resin. Wherenecessary, the above layer (C) comprising the fluorine-containing resinmay contain an electrically conductive material for providing thelaminate with electric conductivity. In this case, the level of additionof the electrically conductive material may be such that electricconductivity can be provided. Thus, the addition level may be asdescribed above.

[0114] The above fluorine-containing resin is not particularlyrestricted but may be any melt-moldable fluorine-containing resin,including, for example, tetrafluoroethylene/fluoro(alkylvinyl ether)copolymers (PFA), tetrafluoroethylene/hexafluoropropylene copolymers(FEP), ethylene/tetrafluoroethylene copolymers (ETFE),polychlorotrifluoroethylene (PCTFE), ethylene/chlorotrifluoroethylenecopolymers (ECTFE), polyvinyl fluoride (PVF) and polyvinylidene fluoride(PVDF). It may be the above-described fluorine-containing ethylenicpolymer. The above fluorine-containing resin may have a melting pointnot lower than 260° C.

[0115] Among them, those having a melt flow rate of 0.5 to 100 g/10minutes at an arbitrarily selected temperature between 230° C. and 300°C. are suited for use in producing multilayer laminates such as fuelpiping tubes and hoses, etc., which retain a low level of liquidagent/fuel permeability and are excellent in flexibility, coldtemperature impact resistance, heat resistance and so forth, bysimultaneous multilayer coextrusion with the polyamide.

[0116] A special feature of the present invention is that afluorine-containing resin having a relatively high melting point, namelya melting point of not lower than 250° C., can be used as theabove-mentioned fluorine-containing resin. While, among the conditionsof extruding fluorine-containing resins, including the above-describedfluorine-containing ethylenic polymer (B), the die temperature alone isrestricted, the melt flow in the die section can be secured by settingthe cylinder temperature at a sufficiently high level, so thatmultilayer laminates having such a constitution can easily be producedby simultaneous multilayer coextrusion. Fluorine-containing resinshaving a high melting point are excellent in chemical resistance andhave low level of liquid agent permeability in proportion to the meltingpoint and can be used with great advantage, in particular, in thosefields in which a high level of liquid agent impermeability is required,for example, for automotive fuel piping.

[0117] The fluorine-containing resin of the above (B) and the resin inthe above layer (C) may be the same or different.

[0118] The present invention is also applicable to the production ofmultilayer laminates in which the layer comprising the above (B) isfurther laminated with a layer (A′) comprising a polyamide in lieu ofthe layer (C) comprising the fluorine-containing resin. Where necessary,the layer (A′) comprising the polyamide may contain an electricallyconductive material for providing electric conductivity. In this case,the polyamide may be the same as or different from the above (A).

[0119] The present invention is further applicable to the productionmethod of multilayer laminates in which the layer (C) comprising afluorine-containing resin and not containing the electrically conductivematerial is further laminated with a layer (D) comprising afluorine-containing resin and containing an electrically conductivematerial. In this case, the level of addition of the electricallyconductive material may be such that electric conductivity can beprovided. Thus, the addition level may be as mentioned above. Any of thefluorine-containing resins mentioned above may be used as thefluorine-containing resin constituting the layer (D), and thefluorine-containing resin may be the same as or different from the resinin the above layer (C), and it may have a melting point of not lowerthan 250° C.

[0120] The production method according to the present inventioncomprises laminating at least the above-described (A) and (B), wherenecessary together with the other layer(s) described above, one over theother in a adhered state using the above-described coextrudingapparatus. On that occasion, the line speed of the laminate may be, forexample, 4 to 20 m/minute. It is also possible to produce lined productsby laminating the multilayer laminate molded by the production method ofthe invention with another substrate.

[0121] The draw down ratio, as expressed in terms of the ratio of thedie opening area to the sectional area of the molded article actuallyobtained, is not particularly restricted. For improving the moldingspeed and preventing the occurrence of “melt fracture”, which is aproblem peculiar to fluorine-containing resins, it may be 4 to 9, forinstance, and even a further higher draw down rate can be employed. Inthe case of a circular die, the draw ratio balance is preferably around1.

[0122] In cases where the molded articles are complicated in shape orform or where the moldings are subjected to heating and bending aftermolding, it is also possible to mold the resins by melt extrusion toform a multilayer laminate and subject the thus-formed multilayerlaminate to 0.01 to 10 hours of heat treatment at a temperature lowerthan the lowest melting point among the melting points of the resinsconstituting the above molding to thereby remove the residual strain inthe molded articles. By employing this production method, it is possibleto remove the residual strain, supposedly allow unreacted substances inthe vicinity of the layer interface to react and thereby furtherincrease the adhesion strength of the multilayer moldingsynergistically. Preferably, the above heat treatment is carried out at60° C. or above, more preferably at 80° C. or above.

[0123] The multilayer laminate obtained by the production method of thepresent invention can have an initial interlayer adhesion strengthbetween the layer comprising the polyamide (A) and the layer comprisingthe fluorine-containing ethylenic polymer (B) of not less than 30 N/cmor, further, not less than 40 N/cm, as shown later herein in the examplesection. Thus, very high and strong adhesion strength levels can beattained. Even when the fluorine-containing ethylenic polymer (B)contains no specific functional groups markedly contributing to theimprovement in adhesion, the above effect is spectacular and, in thisrespect, the technology of the invention is clearly distinguishable fromthe prior art technologies.

[0124] In the practice of the invention, the layer comprising thefluorine-containing ethylenic polymer (B) may have a thickness less than0.5 mm. When a layer better in liquid agent permeability resistance thanthe layer comprising the above (B) is used as the above-mentioned layer(C) or layer (D), the layer comprising the above (B) may be thin. As forthe range, the layer comprising the above (B) may be less than 1.5 timesthe thickness of the layer (C) or, in case that the layer (D) is furtherlaminated, less than 1.5 times the total thickness of the layer (C) andlayer (D). In cases where the layer comprising the above (B) is to serveas an intermediate adhesive layer, it is therefore possible to reducethe thickness of the adhesive layer. This is economically advantageous.

[0125] The production method of the invention can appropriately beapplied to the production of such multilayer laminates as listed below,for example:

[0126] tubes and hoses: automotive fuel piping tubes or hoses,automotive radiator hoses, brake hoses, air conditioner hoses, tubes orhoses for transporting liquid agents, and the like;

[0127] films and sheets: diaphragm pump diaphragms, various packingmembers and like sliding members required to have high chemicalresistance, and the like;

[0128] tanks: automotive radiator tanks, liquid agent storage bottles orbags, containers for chemicals, gasoline tanks, and the like;

[0129] electric wires and cables and pipes: coated wires and cables,coated steel tubes, and the like;

[0130] others: carburetor flange gaskets, fuel pump O rings, likevarious automotive seals, seals in the chemical industry such as sealsin chemical pumps and flow meters, seals in the machinery industry suchas hydraulic instrument seals, and the like.

[0131] Among them, preferred embodiments are, for example, as follows:

[0132] (i) tubes or hoses, in particular automotive fuel piping orliquid agent transporting tubes or hoses, each having an at leasttwo-layer structure comprising, as an outer layer, the layer comprisingthe polyamide (A) and, as an inner layer, the layer comprising thefluorine-containing ethylenic polymer (B) and containing or notcontaining an electrically conductive material;

[0133] (ii) tubes or hoses, in particular automotive fuel piping orliquid agent transporting tubes or hoses, each having an at leastthree-layer structure comprising, as an outer layer, the layercomprising the polyamide (A); as an intermediate layer, the layercomprising the fluorine-containing ethylenic polymer (B); and, as aninner layer, the layer (C) comprising the fluorine-containing resin andcontaining or not containing an electrically conductive material, saidfluorine-containing resin having a melting point not lower than 250° C.;

[0134] (iii) tubes or hoses, in particular automotive fuel piping tubesor hoses, each having an at least three-layer structure comprising, asan outer layer, the layer comprising the polyamide (A); as anintermediate layer, the layer comprising the fluorine-containingethylenic polymer (B); and, as an inner layer, the layer (A′) comprisingthe polyamide and containing or not containing an electricallyconductive material as necessary; and

[0135] (iv) tubes or hoses, in particular automotive fuel piping tubesor hoses, each having an at least four-layer structure comprising, as anouter layer, the layer comprising the polyamide (A); as an intermediatelayer, the layer comprising the fluorine-containing ethylenic polymer(B); as an inner layer, the layer (C) comprising the fluorine-containingresin and not containing the electrically conductive material; and, asan innermost layer, the layer (D) comprising the fluorine-containingresin and containing an electrically conductive material, in which atleast one of the fluorine-containing resin of the layer (C) and thefluorine-containing resin of the layer (D) has a melting point not lowerthan 250° C.

[0136] In the production method according to the invention, themultilayer laminate may have a jacket layer as the outermost layerthereof for the purpose of protection, antifouling, insulation and/orshock absorbance, etc. The jacket layer can appropriately be formed bythe simultaneous coextrusion using a resin or a natural or syntheticrubber, for instance, or in a separate step of covering. It is alsopossible to reinforce the laminate with a metal or the like.

[0137] The multilayer laminate obtainable by the production method ofthe invention is excellent in low level of permeability particularlyagainst liquid agents, namely such liquid agents capable ofdeteriorating polyamide resins as solvents or fuels, for example;organic acids such as acetic acid, formic acid, cresol and phenol;inorganic acids such as hydrochloric acid, nitric acid and sulfuricacid; solutions of alkalis such as sodium hydroxide and potassiumhydroxide; alcohols such as methanol and ethanol; amines such asethylenediamine, diethylenetriamine and ethanolamines; amides such asdimethylacetamide; esters such as ethyl acetate and butyl acetate; fuelssuch as gasoline, light oil and heavy oil, pseudofuels such as Fuel C,and mixed fuels composed of these and a peroxide, methanol, ethanol orthe like; and other organic and inorganic liquids.

BEST MODES FOR CARRYING OUT THE INVENTION

[0138] The following examples illustrate the present invention infurther detail. These examples are, however, by no means limitative ofthe scope of the present invention. In the following examples, variousparameter measurements were carried out in the following manner.

(1) Determination of the Number of Carbonate Groups

[0139] The white powder of each fluorine-containing ethylenic polymerobtained or pieces cut from the melt-extruded pellets prepared therefromwere subjected to compression molding at room temperature to give auniform film having a thickness of 0.05 to 0.2 mm. This film wassubjected to infrared absorption spectrophotometry, and the absorbanceof the carbonate (—OC(═O)O—) carbonyl-due peak (ν_(C═O)) appearing atthe absorption wavelength corresponding to 1809 cm⁻¹ was measured. Thenumber (N) of carbonate groups per 10⁶ main chain carbon atoms wascalculated according to the formula (1) given below:

N=500 AW/εdf   (1)

[0140] A: absorbance of the carbonate (—OC(═O)O—) group-due ν_(C═O)peak;

[0141] ε: molar extinction coefficient of the carbonate (—OC(═O)O—)group-due ν_(C═O) peak [1·cm⁻·mol⁻¹]. ε=170 was employed on a modelcompound basis;

[0142] W: average molecular weight of monomer units as calculated on themonomer composition basis;

[0143] d: film density [g/cm³];

[0144] f: film thickness [mm].

[0145] Infrared absorption spectrometric analysis was carried out usinga Perkin-Elmer FTIR spectrometer 1760X (product of Perkin-Elmer) byperforming scanning 40 times. The baseline of the IR spectrum obtainedwas automatically determined using a Perkin-Elmer Spectrum for WindowsVer. 1.4 C, and the absorbance of the peak at 1809 cm⁻¹ was measured.The film thickness was measured using a micrometer.

(2) Determination of the Number of Carbonyl Fluoride Groups

[0146] A film obtained in the same manner as described above under (1)was subjected to infrared absorption spectrophotometry, and theabsorbance of the carbonyl fluoride (—C(═O)F) carbonyl-due peak (ν_(C═O)) appearing at the wavelength corresponding to 1880 cm⁻¹ was determined.Then, the number of carbonyl fluoride groups was calculated by means ofthe same formula (1) as used above under (1) except that ε=600 wasemployed as the molar extinction coefficient [1·cm⁻¹·cm⁻¹] of thecarbonyl fluoride carbonyl-due ν_(C═O) peak on a model compound basis.

(3) Determination of the Composition of the Fluorine-ContainingEthylenic Polymer

[0147] The determination was carried out by ¹⁹F-NMR analysis.

(4) Melting Point (Tm) Determination

[0148] Using a Seiko DSC apparatus, the temperature was raised at a rateof 10° C./min and the melting peaks were recorded. The temperaturecorresponding to the maximum value was reported as the melting point(Tm).

(5) MFR (Melt Flow Rate) Determination

[0149] Using a melt indexer (product of Toyo Seiki Seisakusho K.K.), theweights (g) of the polymer flowing out through a nozzle with a diameterof 2 mm and a length of 8 mm within a unit time (10 minutes) weremeasured under a load of 5 kg at different temperatures.

(6) Appearance of the Multilayer Tube Inside and Outside Surfaces

[0150] Each tube obtained was cut to give two semicircular sections andthe outer and inner surfaces were evaluated by visual observation orunder a stereoscopic microscope at a magnification up to 50 times, forsurface roughness, foaming and other defects according to the followingcriteria:

[0151] ◯: no defects are observed;

[0152] Δ: some or other defects are observed on less than 2% of thewhole surface;

[0153] ×: some or other defects are observed on 2% or more of the wholesurface.

(7) Multilayer Tube Adhesion Strength Determination

[0154] Test specimens with a width of 1 cm were cut from each tube andsubjected to 180° peel testing at a rate of 25 mm/min on a Tensilonuniversal tester. The mean of five maximum values found on anelongation-tensile strength graph was reported as the interlayeradhesion strength.

(8) Tube Tensile Strength Measurement

[0155] The method described in SAE J 2260 was followed.

(9) Tube Tensile Elongation Measurement

[0156] The method described in SAE J 2260 was followed.

(10) Surface Resistivity Measurement

[0157] The method described in SAE J 2260 was followed.

(11) Tube Cold Temperature Impact Resistance Determination

[0158] The method used was as described in SAE J 2260. The result wasexpressed in terms of the number of tube specimens, out of 10, showing,in the burst test after the falling ball test, a burst pressure of notmore than 75% of that before the falling ball test. Thus, for example,the result “0/10” indicates that all the tubes tested after the fallingball test showed a burst pressure exceeding 75% of that before thefalling ball test.

[0159] The polyamides and fluorine-containing ethylenic polymers used inthe following examples were as follows:

Polyamides

[0160] PA-A: Nylon 12, product of Ube Industries, designated 3030MI1,melting point 172-182° C., containing no plasticizer;

[0161] PA-B: Nylon 12, product of Ube Industries, designated 3030MJ1,melting point 169-179° C., containing a plasticizer;

[0162] PA-C: Nylon 12, product of Ube Industries, designated 3035JU,melting point 166-170° C., containing a plasticizer;

[0163] PA-D: Nylon 12, product of Ube Industries, designated 3035LU,melting point 170-180° C., containing no plasticizer.

Fluorine-Containing Ethylenic Polymers, Fluororesins

[0164] F-A to F-G: Products synthesized in Synthesis Examples 1 to 7 tobe mentioned later herein;

[0165] F-H: Fluororesin Neoflon (registered trademark) ETFE, product ofDaikin Industries, designated EP-521, melting point about 265° C., MFR14.8 (g/10 min, 297° C.);

[0166] F-I: Fluororesin Neoflon (registered trademark) ETFE, product ofDaikin Industries, designated EP-610, melting point about 220° C., MFR26.7 (g/10 min, 297° C.);

[0167] F-J: Fluororesin Neoflon (registered trademark) ETFE containingan electrically conductive material, product of Daikin Industries,designated EP-610AS, melting point about 220° C., MFR 6.8 (g/10 min,265° C.);

[0168] F-K: Melt-moldable fluororesin composite Neoflon (registeredtrademark) FMC, product of Daikin Industries, designated EA-LR43(fluororesin-nylon blend), MFR 6.5 (g/10 min, 235° C.).

SYNTHESIS EXAMPLE 1 Synthesis of Fluorine-Containing Ethylenic PolymerF-A

[0169] An autoclave was charged with 380 L of distilled water and, afterthorough nitrogen purging, charged with 75 kg of1-fluoro-1,1-dichloroethane, 155 kg of hexafluoropropylene and 0.5 kg ofperfluoro(1,1,5-trihydro-1-pentene), and the system inside wasmaintained at 35° C. and at a stirring rate of 200 rpm. Thereafter,tetrafluoroethylene was charged under pressure to 0.7 MPa, followed bycharging of ethylene under pressure to 1.0 MPa. Then, 2.4 kg ofdi-n-propyl peroxydicarbonate was charged to initiate thepolymerization. As the polymerization progressed, the system insidepressure decreased, so that a mixed gas composed oftetrafluoroethylene/ethylene/hexafluoropropylene=40.5/44.5/15.0 molepercent was continuously fed to maintain the system inside pressure at1.0 MPa. As for perfluoro(1,1,5-trihydro-1-pentene), a total of 1.5 kgwas charged continuously. Stirring was continued for 20 hours. Then,after depressurization to atmospheric pressure, the reaction product waswashed with water and dried to give 200 kg of a powder(fluorine-containing ethylenic polymer F-A). The results of analyses ofthis product are shown in Table 1.

SYNTHESIS EXAMPLES 2 AND 3 Synthesis of Fluorine-Containing EthylenicPolymers F-B and F-C

[0170] Fluorine-containing ethylenic polymers F-B and F-C were producedin the same manner as in Synthesis Example 1. The results of analysis ofthese are shown in Table 1.

SYNTHESIS EXAMPLE 4 Synthesis of Fluorine-Containing Ethylenic PolymerF-D

[0171] An autoclave was charged with 400 L of distilled water and, afterthorough nitrogen purging, charged with 320 kg of perfluorocyclobutane,80 kg of hexafluoropropylene, 19 kg of tetrafluoroethylene and 6 kg ofvinylidene fluoride, and the system inside was maintained at 35° C. andat a stirring rate of 180 rpm. Thereafter, 5 kg of di-n-propylperoxydicarbonate was charged to initiate the polymerization. As thepolymerization progressed, the system inside pressure decreased, so thata mixed gas composed of tetrafluoroethylene/vinylidenefluoride/hexafluoropropylene=50/40/10 mole percent was continuously fedto maintain the system inside pressure at a constant level. Stirring wascontinued for 30 hours. Then, after depressurization to atmosphericpressure, the reaction product was washed with water and dried to give200 kg of a powder (fluorine-containing ethylenic polymer F-D). Theresults of analyses of this product are shown in Table 1.

SYNTHESIS EXAMPLE 5 Synthesis of Fluorine-Containing Ethylenic PolymerF-E

[0172] An autoclave was charged with 400 L of distilled water and, afterthorough nitrogen purging, charged with 75 kg of1-fluoro-1,1-dichloroethane, 190 kg of hexafluoropropylene and 1.5 kg ofperfluoro(1,1,5-trihydro-1-pentene), and the system inside wasmaintained at 35° C. and at a stirring rate of 200 rpm. Thereafter,tetrafluoroethylene was charged under pressure to 0.7 MPa, followed bycharging of ethylene under pressure to 1.0 MPa. Then, 2.6 kg ofdi-n-propyl peroxydicarbonate was charged to initiate thepolymerization. As the polymerization progressed, the system insidepressure decreased, so that a mixed gas composed oftetrafluoroethylene/ethylene/hexafluoropropylene=40.5/42.5/17.0 molepercent was continuously fed to maintain the system inside pressure at1.0 MPa. Stirring was continued for 30 hours. Then, afterdepressurization to atmospheric pressure, the reaction product waswashed with water and dried to give 172 kg of a powder. The powderobtained was then extruded at a cylinder temperature of 320° C. using asingle screw extruder (product of Tanabe Practice Kikai, VS 50-24) togive pellets (fluorine-containing ethylenic polymer F-E). The results ofanalyses of this product are shown in Table 1.

SYNTHESIS EXAMPLE 6 Synthesis of Fluorine-Containing Ethylenic PolymerF-F

[0173] The fluorine-containing ethylenic polymer F-B obtained inSynthesis Example 2 was dry-blended with an electrically conductivematerial (acetylene black) in a mixing ratio of 85/15 by weight, and themixture was melted and kneaded in the same manner as in SynthesisExample 5 except that the cylinder temperature was 245° C. The resultsof analyses of the thus-obtained pellets (fluorine-containing ethylenicpolymer F-F) are shown in Table 1.

SYNTHESIS EXAMPLE 7 Synthesis of Fluorine-Containing Ethylenic PolymerF-G

[0174] An autoclave was charged with 9.5 kg of the powder offluorine-containing ethylenic polymer F-B as obtained in SynthesisExample 2, 700 g of 28% ammonia water and 10 L of distilled water, thesystem was heated with stirring, and stirring was continued for 7 hourswhile maintaining the temperature at 80° C. The contents were washedwith water and subjected to drying treatment to give 9.2 kg of a powder.By such treatment, the active functional groups (carbonate groups andcarbonyl fluoride groups) contained in the resin were converted to amidegroups, which are chemically and thermally stable. The quantitativeprogress of such conversion was confirmed by infrared spectrophotometry.The results of analyses of the resin after treatment are shown inTable 1. In Table 1, TFE stands for tetrafluoroethylene, Et forethylene, HFP for hexafluoropropylene, VdF for vinylidene fluoride, andHF-Pe for perfluoro(1,1,5-trihydro-1-pentene). TABLE 1 Number of groupsper 10⁶ main chain Fluorine- carbon atoms MFR containing CarbonylMelting (g/10 min) ethylenic Monomer composition (mole %) Carbonatefluoride point (measurement temp.) polymer TFE Et HFP VdF HF-Pe groupgroup (° C.) (° C.) Synthesis F-A 40.8 44.8 13.9 — 0.5 300 3 162.5  2.6(230) example 1 Synthesis F-B 46.2 43.8 9.5 — 0.5 255 5 194.3  8.9 (230)example 2 Synthesis F-C 47.1 44.1 8.3 — 0.5 189 7 207.4  8.3 (230)example 3 Synthesis F-D 51.3 — 9.8 38.9 — 311 3 169.2 13.8 (230) example4 Synthesis F-E 40.5 45.0 14.0 — 0.5 67 67 170.2 11.3 (230) example 5Synthesis F-F 46.1 43.8 9.6 — 0.5 76 38 196.1  4.2 (265) example 6Synthesis F-G 46.1 43.8 9.6 — 0.5 Not Not 193.5  9.8 (230) example 7detected detected

Multilayer Tube Molding and Evaluation Thereof EXAMPLE 1

[0175] Using a tube extrusion apparatus for three components and threelayers equipped with a spiral multi-manifold die, a tube with an insidediameter of 6 mm and an outside diameter of 8 mm was molded continuouslyby feeding the polyamide PA-A, the fluorine-containing ethylenic polymerF-A and the commercially available electric conductive fluororesin F-Jso that they might form the outer layer, intermediate layer and innerlayer, respectively. The size of the die mandrel was 12 mm/16 mm. Themolding conditions and the results of evaluation of the tube obtainedare shown in Table 2. The flat portion of the die mandrel had a lengthof 50 mm (in the table, referred to as “die length”). TABLE 2 Example 12 3 4 5 6 7 8 9 10 11 12 13 Outer layer resin PA-A PA-A PA-A PA-A PA-APA-A PA-A PA-A PA-A PA-A PA-A PA-A PA-A Intermediate layer resin F-A F-AF-A F-B F-C F-E F-A F-A F-A — — — — Inner layer resin F-J F-J F-J F-JF-J F-J F-I F-I F-H F-A F-D F-F F-F Innermost layer resin — — — — — — —F-J F-J — — — — Cylinder Outer layer 245 245 245 245 245 245 245 245 245245 245 245 245 temp. Intermediate 265 265 265 275 275 265 265 265 265 —— — — (° C.) layer Inner layer 330 330 330 330 330 330 300 300 330 265250 275 275 Innermost — — — — — — — 330 330 — — — — layer Dietemperature (° C.) 280 280 280 280 270 280 280 280 285 280 280 275 275Tube line speed (m/min) 8.0 4.0 12.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.08.0 Thickness Outer layer 0.76 0.76 0.76 0.75 0.74 0.74 0.75 0.75 0.750.70 0.69 0.69 0.69 of each Intermediate 0.10 0.10 0.10 0.09 0.10 0.100.10 0.10 0.10 — — — — layer layer (mm) Inner layer 0.15 0.15 0.15 0.150.15 0.15 0.16 0.10 0.10 0.30 0.30 0.30 0.30 Innermost — — — — — — —0.05 0.05 — — — — layer Die length (mm) 50 50 50 50 50 50 50 50 50 50 5050 50 Tube tensile strength 36 37 31 36 36 35 36 36 33 35 36 35 34 (Mpa)Tube tensileelongation >200 >200 >200 >200 >200 >200 >200 >200 >200 >200 >200 >200 >200(%) Cold temperature impact 0/10 0/10 0/10 0/10 0/10 0/10 0/10 0/10 0/100/10 0/10 0/10 0/10 resistance Appearance of tube in- ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘∘ ∘ ∘ ∘ side and outside Adhesion strength (N/ 40.8 40.2 41.0 39.5 35.832.0 36.1 39.1 40.3 37.4 32.0 30.0 35.0 cm) Surface resistivity 0.040.03 0.06 0.05 0.05 0.05 — 0.1 0.1 — — 0.01 0.01 (MΩ/□)

EXAMPLES 2 AND 3

[0176] Multilayer tubes were molded in the same manner as in Example 1except that the tube line speed was changed. The molding conditions andthe results of evaluation of the tubes obtained are shown in Table 2.

[0177] From these results, it could be confirmed that sufficient levelsof adhesiveness can be attained even when the line speed is changed.

EXAMPLES 4 TO 6 AND COMPARATIVE EXAMPLES 1 AND 2

[0178] Multilayer tubes were molded in the same manner as in Example 1except that the fluorine-containing ethylenic polymer for forming theintermediate layer was changed and the cylinder temperature was changedaccording to that material (Examples 4 to 6 and Comparative Example 1).Further, a multilayer tube was molded in the same manner as in Example 1except that the die temperature was lowered (Comparative Example 2). Themolding conditions and the results of evaluation of the tubes obtainedare shown in Table 2 (Examples 4 to 6) and Table 3 (Comparative Examples1 and 2).

[0179] As these results indicate, high adhesion strength valuesexceeding 30 N/cm were obtained, like in Example 1 where F-A was used,when the fluorine-containing ethylenic polymer F-B, F-C or F-E was usedin forming the intermediate layer. When the fluorine-containingethylenic polymer F-G was used for forming the intermediate layer andthe die temperature was set at 255° C., the multilayer tube showed noadhesion at all between PA-A and F-G. On the other hand, when the dietemperature was raised to 320° C., the foaming of the PA-A layer becameremarkable and no adhesion was found at all between PA-A and F-G. Thesefacts sufficiently evidenced the effects of the present invention. Evenwhen the fluorine-containing ethylenic polymer F-A was used for formingthe intermediate layer, no satisfactory adhesion strength was obtainedbetween that layer and the outer layer when the die temperature was low.

EXAMPLE 7

[0180] A multilayer tube was molded in the same manner as in Example 1except that F-I was used as the fluorine-containing ethylenic polymerfor forming the inner layer and the cylinder temperature was changedaccordingly. The molding conditions and the results of evaluation of thetube obtained are shown in Table 2. As the results shown in Table 2indicate, firm adhesion, like in the case of the use of the conductivefluororesin, was attained even when the non-conductive fluororesin F-1was used for forming the inner layer.

EXAMPLES 8 AND 9

[0181] Using a tube extrusion machine for four components and fourlayers equipped with a spiral multi-manifold die, tubes with an insidediameter of 6 mm and an outside diameter of 8 mm were moldedcontinuously by feeding the polyamide resin PA-A, thefluorine-containing ethylenic polymer F-A, the fluororesin F-I (Example8) or F-H (Example 9) and the conductive fluororesin F-J so that theymight form the outer layer, intermediate layer, inner layer andinnermost layer, respectively. The molding conditions and the results ofevaluation of the tubes obtained are shown in Table 2. As the resultsshown in Table 2 indicate, sufficiently high adhesion strength wasobtained even when the inner layer was composed of two layers. The ETFEhaving a high melting point excellent in fuel impermeability could beextrusion-molded (Example 9) as well.

EXAMPLES 10 TO 13 AND COMPARATIVE EXAMPLES 3 TO 5

[0182] Using a tube extrusion machine for two components and two layersequipped with a spiral multi-manifold die, tubes with an inside diameterof 6 mm and an outside diameter of 8 mm were molded continuously byfeeding the polyamide resin PA-A and the fluorine-containing ethylenicpolymers so that they might form the outer layer and inner layer,respectively. The molding conditions and the results of evaluation ofthe tubes obtained are shown in Table 2 (Examples 10 to 13) and Table 3(Comparative Examples 3 to 5). As the results shown in the tablesindicate, the multilayer tube obtained by using the fluorine-containingethylenic polymer F-G and a die temperature of 255° C. showed noadhesion at all between PA-A and F-G. On the other hand, when the dietemperature was raised to 320° C., the foaming of the PA-A layer wasremarkable and no adhesion was found at all between PA-A and F-G. Thesefacts sufficiently evidenced the effects of the present invention. Evenwhen the fluorine-containing ethylenic polymer F-A was used, nosatisfactory adhesion strength was obtained between the layer thereofand the outer layer when the die temperature was low. When the dietemperature was raised excessively, the external appearance was impaireddue to foaming and so on; in addition, sizing could not be performed,hence any proper multilayer tubes could not be obtained, hence the tubeperformance characteristics could not be measured.

EXAMPLES 14 AND 15 AND COMPARATIVE EXAMPLES 6 AND 7

[0183] Multilayer tubes were molded in the same manner as in Example 1except that the outer layer-forming polyamide was changed. The moldingconditions and evaluation results are shown in Table 3. As the resultsshown in the table indicate, sufficiently high levels of adhesionstrength could be obtained, even when the plasticizer-containingpolyamides were used in lieu of the plasticizer-free ones. On the otherhand, when the die temperature was low, no sufficient adhesion strengthcould be obtained even when the fluorine-containing ethylenic polymerF-A or F-B was used as the intermediate layer, as indicated by theresults in the comparative examples. TABLE 3 Example Comparative example14 15 16 17 1 2 3 4 5 6 7 Outer layer resin PA-B PA-C PA-B PA-A PA-APA-A PA-A PA-A PA-A PA-B PA-C Intermediate layer resin F-A F-A F-A F-AF-G F-A — — — F-A F-B Inner layer resin F-J F-J F-J F-J F-J F-J F-G F-AF-A F-J F-J Innermost layer resin — — — — — — — — — — — Cylinder temp.Outer layer 245 245 245 245 245 245 245 245 245 245 245 (° C.)Intermediate layer 265 265 265 265 265 265 — — — 275 265 Inner layer 330330 330 330 330 330 250 265 265 330 330 Innermost layer — — — — — — — —— — — Die temperature (° C.) 280 280 280 280 255 245 255 245 320 245 250Tube line speed (m/min) 8.0 8.0 20.0 4.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0Thickness of Outer layer 0.76 0.76 0.76 0.76 0.75 0.75 0.69 0.70 0.700.75 0.75 each layer Intermediate layer 0.10 0.10 0.10 0.10 0.11 0.11 —— — 0.11 0.09 (mm) Inner layer 0.15 0.15 0.15 0.15 0.15 0.15 0.30 0.300.30 0.15 0.15 Innermost layer — — — — — — — — — — — Die length (mm) 5050 50 50 50 50 50 50 50 50 50 Tube tensile strength (Mpa) 37 39 31 35 3534 35 33 Not 34 38 measurable Tube tensile elongation(%) >200 >200 >200 >200 >200 >200 >200 >200 Not >200 >200 measurableCold temperature impact resistance 0/10 0/10 0/10 0/10 0/10 0/10 0/100/10 Not 0/10 0/10 measurable Appearance of tube inside and outside ∘ ∘∘ ∘ ∘ ∘ ∘ ∘ X ∘ ∘ surface Adhesion strength (N/cm) 40.1 39.0 40.1 43.97.2 15.0 11.0 12.1 Not 12.4 16.2 measurable Surface resistivity (MΩ/□)0.04 0.04 0.08 0.03 0.05 0.05 — — — 0.05 0.06

[0184] Example 14 except that the line speed was set at 20 m/minute andthe mandrel size was changed to 18 mm/24 mm. The molding conditions andevaluation results are shown in Table 3. From the table, it is seen thatsufficiently firm adhesion could be obtained even when the draw downratio was increased.

EXAMPLE 17

[0185] A multilayer tube was molded in the same manner as in Example 2except that the length of the flat section of the die mandrel was 200mm. The molding conditions and evaluation results are shown in Table 3.From the table, it is seen that a sufficient adhesion strength could beobtained even when the length of the flat portion was increased.

EXAMPLES 18 AND COMPARATIVE EXAMPLES 8 AND 9 Multilayer Blow-MoldedContainers and Evaluation Thereof

[0186] Using a blow molding machine for two components and two layersequipped with a die having a die diameter of 12 mm and a core diameterof 8.5 mm together with a feed block, cylindrical molded articles havinga diameter of 40 mm and a height of 300 mm were molded. The moldingconditions and the results of evaluation of the molded articles obtainedare shown in Table 4. The adhesion strength was measured along thelongitudinal direction of the cylinder side. As seen from the table,sufficiently firm adhesion strength could be obtained.

[0187] On the other hand, attempts were made to mold multilayercontainers by blow molding in the same manner as in Example 18 exceptthat the feed block and die temperatures were each set at 250° C. Thecontainers obtained were inferior in interlayer adhesion strength(Comparative Example 8). Therefore, the feed block and die temperatureswere each raised, whereupon, at 320° C., the melt viscosity of thepolyamide, in particular, markedly lowered and any cylindrical parisoncould not be molded due to the draw down phenomenon (Comparative Example9). TABLE 4 Comparative Example example 18 8 9 Outer layer resin PA-DPA-D PA-D Inner layer resin F-A F-A F-A Cylinder temp. Outer layer 235235 235 (° C.) Inner layer 240 240 240 Die temperature (° C.) 275 250320 Feed block temperature (° C.) 275 250 320 Thickness of Outer layer0.70 0.69 — each layer Inner layer 0.30 0.30 — (mm) Adhesion strength(N/cm) 30.9 10.1 —

Industrial Applicability

[0188] The present invention, which has the constitution describedabove, can markedly improve the interlayer adhesion strength ofmultilayer laminates, in particular the interlayer adhesion strengthbetween a polyamide and a fluorine-containing ethylenic polymer, ascompared with the prior art production methods in a simple and easymanner. Furthermore, the adhesion strength of the multilayer laminate asa whole can be markedly improved by using a fluorine-containingethylenic polymer having carbonyl groups, without requiring anyadditional step, and a multilayer laminate excellent in cold temperatureimpact resistance can be produced by simultaneous multilayer coextrusionusing a commercially available polyamide. Therefore, the molding can beprovided with good mechanical properties and high-level durability in anexternal environment, for example against heat and various chemicalsubstances, by disposing such a polyamide as an outer layer and, inaddition, a multilayer laminate can economically be produced bydisposing a fluorine-containing resin layer as the innermost layer tothereby provide the molding with those heat resistance, oil resistance,chemical resistance and low level of liquid agent permeability which thefluorine-containing resin has. This is very advantageous from theindustrial point of view.

1. A production method of a multilayer laminate which compriseslaminating at least a polyamide (A) and a fluorine-containing ethylenicpolymer (B) by simultaneous multilayer coextrusion using a coextrusionapparatus to obtain the laminate comprising said polyamide (A) and saidfluorine-containing ethylenic polymer (B), said coextrusion apparatuscomprising a die and a plurality of extruders for feeding resins to saiddie, and the temperature of said die being set within the rangeexceeding 260° C. but not higher than 310° C.
 2. The production methodaccording to claim 1, wherein the temperature of a feed block, in casethat the feed block is connected to the die, is also set within therange exceeding 260° C. but not higher than 310° C.
 3. The productionmethod according to claim 1 or 2, wherein a cylinder temperature of theextruder for feeding the polyamide (A) to the die is set at a levelhigher by 20 to 90° C. than the melting point of the polyamide (A) 4.The production method according to claim 1 or 2, wherein the temperatureof the polyamide (A) at a resin inlet of the die, or of the feed blockin case that the feed block is connected to the die, is set at a levelhigher by 20 to 90° C. than the melting point of the polyamide (A), saidresin inlet being connected to the extruder.
 5. The production methodaccording to any of claims 1 to 4, wherein the fluorine-containingethylenic polymer (B) is a fluorine-containing ethylenic polymer havinga carbonyl group.
 6. The production method according to any of claims 1to 5, wherein the polyamide (A) is nylon 11 or nylon
 12. 7. Theproduction method according to any of claims 1 to 6, wherein thecarbonyl group content of the fluorine-containing ethylenic polymer (B)having the carbonyl group is 3 to 1,000 groups, in total, per 1×10⁶ mainchain carbon atoms.
 8. The production method according to any of claims1 to 7, wherein the fluorine-containing ethylenic polymer (B) is atleast one species selected from the group consisting of: (I) copolymersresulting from polymerization at least of 5 to 95 mole percent oftetrafluoroethylene and 95 to 5 mole percent of ethylene; (II)copolymers resulting from polymerization at least of 3 to 97 molepercent of tetrafluoroethylene and 97 to 3 mole percent of a compoundrepresented by the general formula CF₂═CF-Rf¹ in the formula, Rf¹represents CF₃ or ORf² and Rf² represents a perfluoroalkyl group having1 to 5 carbon atoms; (III) copolymers resulting from polymerization atleast of: a. 20 to 90 mole percent of tetrafluoroethylene; b. 10 to 80mole percent of ethylene; and c. 1 to 70 mole percent of a compoundrepresented by the general formula: CF₂═CF-Rf¹ in the formula, Rf¹represents CF₃ or ORf² and Rf² represents a perfluoroalkyl group having1 to 5 carbon atoms; (IV) copolymers resulting from polymerization of atleast vinylidene fluoride; and (V) copolymers resulting frompolymerization at least of: d. 15 to 60 mole percent of vinylidenefluoride; e. 35 to 80 mole percent of tetrafluoroethylene; and f. 5 to30 mole percent of hexafluoropropylene.
 9. The production methodaccording to any of claims 1 to 8, wherein the fluorine-containingethylenic polymer (B) has a melting point of 150 to 270° C.
 10. Theproduction method according to any of claims 1 to 9, wherein the initialinterlayer adhesion strength between a layer comprising the polyamide(A) and a layer comprising the fluorine-containing ethylenic polymer (B)of the multilayer laminate is not less than 20 N/cm.
 11. The productionmethod according to any of claims 1 to 10, wherein the multilayerlaminate is selected from the group consisting of films, sheets,profiles, pipes, hoses, tubes, bottles and tanks.
 12. The productionmethod according to claim 11, wherein the multilayer laminate is anautomotive fuel piping tube or hose each having an at least three-layerstructure comprising, as an outer layer, a layer comprising thepolyamide (A); as an intermediate layer, a layer comprising thefluorine-containing ethylenic polymer (B); and, as an inner layer, alayer (C) comprising a fluorine-containing resin and containing or notcontaining an electrically conductive material, said fluorine-containingresin having a melting point of not lower than 250° C.
 13. Theproduction method according to claim 11, wherein the multilayer laminateis an automotive fuel piping tube or hose each having an at leastfour-layer structure comprising, as an outer layer, a layer comprisingthe polyamide (A); as an intermediate layer, the layer comprising thefluorine-containing ethylenic polymer (B); as an inner layer, a layer(C) comprising a fluorine-containing resin and not containing anelectrically conductive material; and, as an innermost layer, a layer(D) comprising a fluorine-containing resin and containing anelectrically conductive material, at least one of thefluorine-containing resin of the layer (C) and the fluorine-containingresin of the layer (D) having a melting point of not lower than 250° C.14. The production method according to any of claims 1 to 13, wherein adraw down ratio is 4 to
 9. 15. An automotive fuel piping tube or hoseeach having an at least three-layer structure comprising, as an outerlayer, a layer comprising a polyamide (A); as an intermediate layer, alayer comprising a fluorine-containing ethylenic polymer (B); and, as aninner layer, a layer (C) comprising a fluorine-containing resin andcontaining or not containing an electrically conductive material,wherein said fluorine-containing resin has a melting point of not lowerthan 250° C.
 16. An automotive fuel piping tube or hose each having anat least four-layer structure comprising, as an outer layer, a layercomprising a polyamide (A); as an intermediate layer, a layer comprisinga fluorine-containing ethylenic polymer (B); as an inner layer, a layer(C) comprising a fluorine-containing resin and not containing anelectrically conductive material; and, as an innermost layer, a layer(D) comprising a fluorine-containing resin and containing anelectrically conductive material, wherein at least one of thefluorine-containing resin of the layer (C) and the fluorine-containingresin of the layer (D) has a melting point of not lower than 250° C.